Bending machines

ABSTRACT

This invention relates to machines for bending metal workpiece strips to form a road vehicle bumper bar having a central portion and two convex-curved end portions. The machine comprises a frame, a two-part die having a central portion and two convexcurved portions, said die being divided in the central portion to provide two similar die halves, and first mounting means for mounting the die halves on the frame for rotation about parallel axes. The machine additionally comprises first power operated means to rotate said half-dies about their axes of rotation. The machine comprises two shoes, each of which is co-operative with a respective half-die in the vicinity of the convex-curved portion thereof, second mounting means for mounting said shoes on the frame for traversing movement relative to the half-dies, and second power operated means associated with each of the shoes and operative to urge the shoes towards their respective half-dies to trap a workpiece strip between the half-dies and the shoes. Power operated traversing means are provided to cause the shoes to traverse around the convex-curved portions of their respective half-dies, and the machine comprises compensating means associated with each shoe and its associated power operated means to minimise the work done by the power operated traversing means in causing the shoes to traverse around the convex-curved portions of the half-dies.

United States Patent [1 1 Holden [4 1 Sept. 3, 1974 BENDING MACHINES [22] Filed: Mar. 12, 1973 [21] Appl. No.: 340,637

[30] Foreign Application Priority Data Mar. 15, 1972 Great Britain 12010/72 [52] US. Cl 72/383, 72/306, 72/308, 72/381, 72/395, 72/399 [51] Int. Cl B21d 5/02 [58] Field of Search 72/306, 308, 310, 378, 72/383, 395, 399, 403, 381

[56] References Cited UNITED STATES PATENTS 1,811,259 6/1931 Curtis 72/399 2,571,471 10/1951 Neely 72/399 2,880,780 4/1959 Mackey 72/151 2,986,194 5/1961 Marco 72/297 3,561,248 2/1971 Bessbo 72/383 3,595,061 7/1971 Bessbo 72/383 Primary Examiner-C. W. Lanham Assistant ExaminerJames R. Duzan Attorney, Agent, or Firm-A. Yates Dowell, Jr.

[57 ABSTRACT This invention relates to machines for bending metal workpiece strips to form a road vehicle bumper bar having a central portion and two convex-curved end portions. The machine comprises a frame, a two-part die having a central portion and two convex-curved portions, said diebeing divided in the central portion to provide two similar die halves, and first mounting means for mounting the die halves on the frame for rotation about parallel axes. The machine additionally comprises first power operated means to rotate said half-dies about their axes of rotation.

The machine comprises two shoes, each of which is co-operative with a respective half-die in the vicinity of the convex-curved portion thereof, second mounting means for mounting said shoes on the frame for traversing movement relative to the half-dies, and second power operated means associated with each of the shoes and operative to urge the shoes towards their respective half-dies to trap a workpiece strip between the half-dies and the shoes.

8 Claims, 10 Drawing Figures PATENTEUSEFS m4 SHEEI 30? 7 Fll @lll

PATENTEDSEPS I974 sum Sat 1 PATENTED8EP3 M I 3.832.879

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PATENTEDSEP3 1974 398328879 I SHEET 7 OF 7 FIOWO BENDING MACHINES BACKGROUND OF THE INVENTION A known bending machine for making road vehicle bumper bars comprises a die, having a central portion and two convex-curved portions, and two shoes mounted for traversing movement in which said shoes press opposite end portions of a metal workpiece strip progressively against the convex-curved portions of the die to cause the strip to be conformed to the shape of the dies. Thus, such machines comprise power operated means to urge each shoe towards the die, and power operated traversing means to cause the shoes to move over the workpiece strip.

The curved end portions of a bumper bar are seldom of a single curvature, but may, for example, be of progressively increasing curvature towards the ends thereof.

Desirably, each shoe is mounted for swinging movement about an axis at a position close to the mean centre of curvature of one end portion of the die. However, with the shoes so mounted about such an axis, during traversing movement the shoe will move away from said axis, due to the varying curvature of the bumper bar, and against the force applied to the shoe by the power operated means.

Thus, traversing of the shoes would require that a considerable amount of work be done, and this would necessitate the use of powerful traversing means.

SUMMARY OF THE INVENTION According to the present invention a machine is provided for bending a metal workpiece strip to form a road vehicle bumper bar having a central portion and two convex-curved end portions, said machine comprising a frame; a two-part die having a central portion and two convex-curved portions, said die being divided in the central portion to provide two similar half-dies; first mounting means mounting the half-dies, on the frame for rotation about parallel axes; first power operated means to rotate said half-dies about their axes of rotation; two shoes each of which is co-operative with a respective half-die in the vicinity of the convexcurved portion thereof; second mounting means for mounting said shoes on the frame for traversing movement relative to the half-dies; second power operated means associated with each of the shoes and operative to urge the shoes towards their respective half-dies to trap a workpiece strip between the half-dies and the shoes; and power operated traversing means to cause the shoes to traverse around the convex-curved portions of their respective half-dies; the machine comprising compensating means associated with each shoe and its associated power operated means to minimise the work done by the power operated traversing means in causing the shoes to traverse around the convex-curved I portions of the half-dies.

Preferably the compensating means operates to minimise movement of the regions of engagement between each shoe, or parts carried thereby, and the second power operated means, or parts carried thereby, in a direction against that of the force applied by said second power operated means against the shoe. Advantageously said compensating means comprises cam means, and a pressure roller which in the operation of the machine are urged into engagement.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be more particularly described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a front elevation of a bending machine in a substantially initial or starting position but from which dies and other parts have been removed for clarity of illustration,

FIG. 2 is an end view of FIG. 1 looking in the direction of the arrow 2,

FIG. 3 is a plan view of FIG. 1,

FIG. '4 is a fragmentary plan view similar to FIG. 3 but also showing a half-die and a shoe associated therewith and in the initial or starting position,

FIG. 5 is a diagrammatic plan view of the machine in the initial or starting position,

FIGS. 6 to 9 are diagrammatic plan views showing the various operations performed to make the road vehicle bumper bar, and,

FIG. 10 is a diagrammatic plan view showing a modification of the bending machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 6 there is indicated at 20 a straight metal workpiece strip of trough-shaped cross-section as indicated at 20a from which a finished road vehicle bumper bar 20b, see FIGS. 8 and 9, is made in stages and of which the cross-section remains trough-shaped. The finished bumper bar comprises in plan view a central longitudinal slightly curved convex portion 22 and two wrap-around convex corner end portions 24.

The bending machine comprises a main frame 26 of which the upper part is of somewhat C-shaped formation as shown in FIG. 2 to provide a bed part 28 and an overarm part 30 between which an open front or gap 32 is provided.

The bending machine comprises two bending units generally indicated at 33 and disposed on opposite sides of a central axis A-A and the two units are similar with the exception that one is a left-hand unit and the other is a right-hand unit and therefore except where necessary, one unit only will be described as representative of both units.

The two units 33 each afford a two-part die 34 having a central longitudinal portion 34a and two convex curved comer end portions 34b said die being divided in the central portion at 340 to provide two similar halfdies 34d and said half-dies are of effective convex cross-sectional shape as shown in FIG. 2, complementary to the internal trough cross-sectional shape of the bumper bar 20 illustrated in chain dotted lines in FIG.

The bed 28 and overarm 30 afford lower and upper horizontal slide-ways 36, 38 respectively of which the longitudinal axis is indicated at B-B in FIG. 3 and mounted in the slide-ways are slides 40 which can be urged towards and away from the central axis A-A by upper and lower hydraulic piston and cylinder devices diagrammatically illustrated at 42 in FIG. 1.

Mounted in a slide 40 at an outer end thereof and between upper and lower parts 40a thereof is a vertical post 44 upon which an inner sleeve 46 is rotatably mounted by anti-friction bearings and secured to upper and lower ends of the inner sleeve are upper and lower slide-way plates 48 which form an arm 50 which is rotatable about the vertical axis C-C of the post 44 and which vertical axis CC intersects the axis BB, see FIG. 3.

An outer sleeve 52 is rotatably mounted upon the inner sleeve 46 through anti-friction bearings so that said outer sleeve is rotatable about the axis CC.

The half-die 34d is mounted on the outer sleeve 52 and is located between upper and lower cylindrical capstans 54 which are located between upper and lower cam capstans 56 which are secured to the halfdie 34d and are located between the upper and lower slide-way plates 48 and said half-die 34d and cylindrical and cam capstans 54 and 56 respectively are mounted on the cylindrical outer sleeve so as to have a good runfit engagement therewith and so as to be rotatable relative to the outer sleeve about the axis CC.

Disposed between the upper and lower slide-way plates 48 is a shoe 58 having a concave die face 60 of concave cross-sectional formation which is comple mentary to the external cross-sectional formation of the finished bumper bar 20, see FIG. 2, and said die face 60 is straight in a direction longitudinally of the shoe as shown in FIG. 4 and is co-operative with the half die 34d through the workpiece strip 20. The shoe 58 is mounted between upper and lower retraction members 62 which are pivotedto the upper and lower ends of a vertical spindle 64 mounted in upper and lower parts of a slide 66 which is slidably mounted longitudinally in the upper and lower slide-way plates 48 of the arm 50 and said slide 66 is coupled to the piston 68 of a hydraulically operated piston and cylinder device 70 of which the cylinder is supported by the arm 50 so that said device constitutes a power means of the machine operative to urge the shoe 58 towards the half die 34d.

Secured to the back of the shoe and therefore forming a rigid part thereof is a cam block 72 formed with a compensating means provided by a cam formation 74 of which the shape as diagrammatically shown in plan view in FIG. 4 is dependent upon the precise shape, in plan view, of the convex curved corner end portion 34b of the half-die 34d and co-operative with the cam formation 74 is a roller 76 which constitutes a pressure means and said roller is rotatably mounted on the spindle 64 so as to be rotatable about a vertical axis and said roller can be biased by the power means device 70 against the cam formation 74 so that the shoe 58 can be urged towards the half-die 34d to trap the workpiece strip therebetween.

The shoe 58 is supported in a longitudinal direction by two flexible tension members 78 and 80. The flexible tension member 78 is formed by two steel cables mounted in grooves in the upper and lower cam capstans 56 and one end of each cable is connected at 82 to the trailing end of the shoe 58 and the other end of each cable is adjustably connected to a bracket 84 secured to the half-die 34d. The other flexible tension member 80 is formed of upper and lower steel cables which are located in grooves in the upper and lower cylindrical capstans 54 and one end of each cable is connected at 86 to the leading end of the shoe 58 and the other end of each cable is connected to a piston rod 88 of a hydraulic piston and cylinder device 90 which is connected at 92 to the stationary main frame 26 of the machine. Hydraulic pressure can be supplied in a manner not shown to the end of the cylinder of the device 90 adjacent the flexible tension member 80 so that the piston in the cylinder is biased and said member is tensioned. It should be appreciated that the two flexible tension members 78 and 80 in effect cross over each other around the cam and cylindrical capstans 56 and 54 respectively and that during the operation of the shoe 58, hereinafter to be described, said members remain in tension and slack is not allowed to develop in these members.

As before stated, the arm 50 is secured to the inner sleeve 46 and a bracket 94, see FIG. 2, is secured to the arm and is engaged by a driving dog 96 which forms an output member of a torque motor 98 mounted on the slide 40 adjacent the lower end of the post 44 and said motor constitutes a flow-forming power operated traversing means whereby the arm 50 and thus the shoe 58 can be moved around the convex curved corner end portion 34b of the half-die 34d from the initial or starting position of the arm shown in FIGS. 4 and 6 into a final position shown in FIG. 9.

The longitudinal portion of the half-die 34d is pivotally connected at 100 to one end of an adjustable length link 102 of which the other end is pivoted at 104 to one end of a cross-head 106 at one side of the axis A-A, see FIG. 4, so that both half-dies 34d are connected to the common cross-head 106 which is connected to a ram 108 of a hydraulically operated ram device 110 which forms a stretch-forming power operated means whereby the two half-dies 34d can be rotated about the vertical axes CC and the cylinder of the ram device 110 is secured to the stationary frame 26.

One mode of operation of the machine will now be described. The piston and cylinder devices 42 are operated to urge the two slides 40 apart up to stops (not shown) so that the two posts 44 are in their outer spaced apart positions as shown in FIGS. 5 and 6 and the stretch-forming ram device 110 is retracted to cause the two half-dies 34d to assume the initial positions shown in FIGS. 5 and 6. The two piston and cylinder power operated means 70 are also retracted so that the two shoes 58 are spaced from the two half-dies 34d to enable the longitudinally straight but trough crosssectioned workpiece strip 20 to be inserted between the two half-dies and the two shoes whereupon said devices 70 are operated to urge the two shoes towards the respective half-dies to trap the workpiece therebetween whilst the two arms 50 are disposed in their inner initial or starting positions and the pressure means rol- Iers 76 are disposed adjacent the trailing ends of the shoes. The stretch-forming ram device 110 is then extended to cause the left-hand and right-hand half-dies 34d as viewed in FIGS. 5 and 6 to partially rotate in clockwise and anti-clockwise directions respectively about the vertical axes CC of the post 44 and as the workpiece strip 20 is effectively gripped between the shoes 58 and half-dies 34d, the central longitudinal portion of the workpiece strip 22 is subjected to a stretchforming operation until the extension of the ram device 110 finishes and at the end of the stretch-forming operation, the arms 50 assume the approximate positions indicated in FIG. 7.

The two flow-forming torque motors 98 are then operated to partially rotate the left-hand and right-hand arms 50 as viewed in FIG. 9 in clockwise and anticlockwise directions respectively and the rotation of the arms 50 cause the shoes 58 to traverse around the convex curved comer end portions 34b of the half-dies and bend or flow-fonn the end portions of the bumper bar workpiece strip into the wrap-around convex curved corner end portions 24.

The vertical axis C--C of each post 44 is close to the mean axis of curvature 112 of the convex-curved portion 34b of its associated half-die. Specifically, said axis 112 is between the axis C-C and the bumper bar, (see FIG. 6).

From the starting position, during a first part of traverse of the shoe 58, the distance between the axis of the post 44 and the line of engagement the shoe and the workpiece strip decreases (see FIG. 4), and during a second part of traverse of the shoe, this distance increases. Without the provision of said compensating means, said second part of traverse of the shoe would be accomplished with difficulty, since the torque motor 98 would be required to do the work involved in moving the piston 68 against the force applied thereto by the device 70.

However, the cam block 72 is so arranged that, during said first part of traverse of the shoe, the roller rides up the cam formation 74, retaining the distance between the axis of the roller and the axis of the post 44 substantially constant, or decreasing only slightly. During the second part of traverse of the shoe, the roller rides down the cam formation 74, effectively compensating for the increase in the distance between the axis of the post 44 and the line of engagement between the shoe 58 and the workpiece strip.

With certain configurations of bumper curvature, it is possible that the pressure roller 56 moves downhill, or level, throughout traverse of the shoe. However, with certain configurations it may be necessary for the roller 56 to move slightly uphill In any of these three cases, due to the provision of the compensating means, the torque output required of the flowforming torque motor 98 is substantially less than would be required if the compensating means was not provided.

The provision of the flexible tension members 78 and 80 which are relatively crossed-over around the capstans 56 and 54 and are anchored to opposite ends of the shoe 58, ensure that the mean arc of traverse of the shoe is close to the innermost edges of the trough crosssection of the bumper bar so that the shoe tends to slip forwardly relative to the bumper bar over substantially the entire radial width between said radially innermost edges and radially outermost part of the bumper bar, ie at the base of the trough, so that the thickness of the metal of the bar around the convex curved corner end portions 24 thereof tends to be thinned between said radially innermost and radially outermost parts of the corner end portions during the flowforming operations. A similar effect could be obtained by providing a toothed pinion arrangement on the capstans and a toothed rack on the shoe and engaging the rack with the pinion along an arc corresponding approximately to the arc of the radially innermost edges of the corner end portions 24 of the bumper bar.

It should be appreciated that in the mode of operation of the machine described above, the stretchforming of the central longitudinal portion 22 of the bumper bar was performed before the flow-forming operations on the end portions 24 of the bumper bar but alternatively the sequence of operations can be reversed so that the flow-forming operations are performed before the stretch-forming operations or as a further alternative the stretch-forming and flowforrning operations can be performed simultaneously. Whichever sequence of operations is performed by the machine, the gripping pressure applied to the workpiece strip 20 is exerted by the same shoes 58 and halfdies 34d for both the stretch-forming and flow-forming operations so that the finished bumper bar is remarkably free of markings such as are formed when the stretch-forming and flow-forming operations are performed in separate machines.

Instead of the cam fonnation 74 being formed at the back of the shoe 58 and a cylindrical roller 76 being provided to engage the cam formation, the roller 76 may be of cam formation and engage a rectilinear, i.e. straight back formation of the shoe or alternatively the roller and the back formation of the shoe may both be of suitable cam-shaped formation.

In order to remove the finished bumper bar from the machine, the hydraulic cylinder devices 42 are operated to urge the slides 40 inwardly towards each other into their inner positions so that the curved end portions 24 of the bumper bar are freed from the curved end portions 34b of the half-dies 34d and the hydraulic pressure devices are operated so as to withdraw the shoes 58 radially outwardly along the arms 50 so that the positions shown in FIG. 9 are achieved in which the finished bumper bar can be manually removed from the machine.

Referring to FIG. 10, when a bumper bar 20 is required to have two concave or reverse bends 114 in the longitudinal central portion 22, the half-dies 34d are suitably formed and a further suitably formed die 116 is movable by a hydraulic ram device 118 into engagement with the bumper bar after the stretch-forming operation has been performed on the central longitudinal portion 22 of said bumper bar to form the reverse.

bends 114 and subsequently the die 116 is retracted by the ram device 118.

For convenience of illustration the various fluid pressure pipe connections are not shown.

We claim:

1. A machine for bending a metal workpiece strip to form a road vehicle bumper bar having a central portion and two convex-curved end portions, said machine comprising a frame;

a two-part die (34) having a central portion (34a) and two convex-curved portions (34b), said die being divided in the central portion to provide two similar half-dies (34d);

first mounting means mounting the half-dies on the frame for rotation about parallel axes;

first power operated means to rotate said halfdies about their axes of rotation;

two shoes (58) each of which is co-operative with a respective half-die in the vicinity of the convexcurved portion thereof;

second mounting means for mounting said shoes on the frame for traversing movement relative to the v 7 the machine comprising compensating means associated with each shoe and its associated power operated means to minimise the work done by the power operated traversing means in causing the shoes to traverse around the convex-curved portions of the half-dies.

2. A machine according to claim 1 wherein said compensating means operates to minimise movement of the regions of engagement between each shoe, or parts (74) carried thereby, and the second power operated means, or parts (76) carried thereby, in a direction against that of the force applied by said second power operated means against the shoe.

3. A bending machine according to claim 2 wherein the compensating means comprises cam means (74) associated with each shoe, and a pressure roller (76) urged against said cam means by said second power operated means (70) to urge the shoes towards their respective half-dies.

4. A machine according to claim 1 wherein said second mounting means is so arranged that the mean arc of traverse of each shoe is close to the innermost edges of the trough-section of the bumper bar so that, during traverse of the shoe, said shoe moves forwardly relative to the workpiece over substantially the whole of the radial width of the workpiece.

5. A machine according to claim 1 wherein the second mounting means comprises flexible tension members (78, of which one is connected to a trailing end portion (82) of the shoe and another is connected to a leading end portion (86) of the shoe, said flexible tension means crossing each other and being anchored, at opposite end portions thereof, at positions 92) such as to enable the shoe to roll or rock around the convex-curved portion (34b) of its associated half-die (34d) to effect a flow-forming operation.

6. A machine according to claim 5 wherein the flexible tension member (78) connected to the trailing end portion (82) of said shoe is relatively inextensible, and the other flexible tension member (80) connected to the leading end portion (86) of the shoe is connected to biasing means to take up slack.

7. A machine according to claim 6 wherein the flexible tension member (78) passes around a cam-shaped capstan (56) and the flexible tension member (80) passes around a circular capstan (54).

8. A machine according to claim ll wherein each shoe and power operated means associated therewith to urge the shoe towards its associated half-die, are

mounted on an arm which is rotatable about an axis (C--C) at least adjacent the axis (112) of the mean curvature of the respective convex'curved portion, said arm being connected to the power operated traversing means so as to be rotated thereby to subject the workpiece strip to a flow-forming operation. 

1. A machine for bending a metal workpiece strip to form a road vehicle bumper bar having a central portion and two convex-curved end portions, said machine comprising a frame; a two-part die (34) having a central portion (34a) and two convex-curved portions (34b), said die being divided in the central portion to provide two similar half-dies (34d); first mounting means mounting the half-dies on the frame for rotation about parallel axes; first power operated means (110) to rotate said half-dies about their axes of rotation; two shoes (58) each of which is co-operative with a respective half-die in the vicinity of the convex-curved portion thereof; second mounting means for mounting said shoes on the frame for traversing movement relative to the half-dies; second power operated means (70) associated with each of the shoes and operative to urge the shoes towards their respective half-dies to trap a workpiece strip (20) between the half-dies and the shoes; and power operated traversing means (98) to cause the shoes to traverse around the convex-curved portions of their respective half-dies; the machine comprising compensating means associated with each shoe and its associated power operated means to minimise the work done by the power operated traversing means in causing the shoes to traverse around the convex-curved portions of the half-dies.
 2. A machine according to claim 1 wherein said compensating means operates to minimise movement of the regions of engagement between each shoe, or parts (74) carried thereby, and the second power operated means, or parts (76) carried thereby, in a direction against that of the force applied by said second power operated means against the shoe.
 3. A bending machine according to claim 2 wherein the compensating means comprises cam means (74) associated with each shoe, and a pressure roller (76) urged against said cam means by said second power operated means (70) to urge the shoes towards their respective half-dies.
 4. A machine according to claim 1 wherein said second mounting means is so arranged that the mean arc of traverse of each shoe is close to the innermost edges of the trough-section of the bumper bar so that, during traverse of the shoe, said shoe moves forwardly relative to the workpiece over substantially the whole of the radial width of the workpiece.
 5. A machine according to claim 1 wherein the second mounting means comprises flexible tension members (78, 80) of which one is connected to a trailing end portion (82) of the shoe and another is connected to a leading end portion (86) of the shoe, said flexible tension means crossing each other and being anchored, at opposite end portions thereof, at positions (84, 92) such as to enable the shoe to roll or rock around the convex-curved portion (34b) of its associated half-die (34d) to effect a flow-forming operation.
 6. A machine according to claim 5 wherein the flexible tension member (78) connected to the trailing end portion (82) of said shoe is relatively inextenSible, and the other flexible tension member (80) connected to the leading end portion (86) of the shoe is connected to biasing means (90) to take up slack.
 7. A machine according to claim 6 wherein the flexible tension member (78) passes around a cam-shaped capstan (56) and the flexible tension member (80) passes around a circular capstan (54).
 8. A machine according to claim 1 wherein each shoe and power operated means associated therewith to urge the shoe towards its associated half-die, are mounted on an arm which is rotatable about an axis (C-C) at least adjacent the axis (112) of the mean curvature of the respective convex-curved portion, said arm being connected to the power operated traversing means so as to be rotated thereby to subject the workpiece strip to a flow-forming operation. 